JP2011122211A - Mist cooling apparatus, heat treatment apparatus and mist cooling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mist cooling apparatus, a heat-treatment apparatus and a mist cooling method with which a material to be treated can be cooled in the wide range of cooling speed. <P>SOLUTION: In the mist cooling apparatus 3, a heated material M to be treated is cooled by injecting the mist for cooling to the material M. The device has a constitution having a first nozzle 35 injecting the mist for cooling and a second nozzle 45 injecting the mist for cooling, the mist having a smaller particle diameter than the particle diameter of the mist for cooling injected from the first nozzle 35. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

 The present invention relates to a mist cooling device, a heat treatment device, and a mist cooling method.

 Patent Document 1 discloses a mist cooling device that is used for heat treatment of an object to be processed such as metal and cools the object to be processed. Since the mist cooling device injects a mist-like cooling liquid onto the heated workpiece and performs cooling by the latent heat of vaporization of the cooling liquid, its cooling capacity is higher than that of a conventional gas injection type cooling device. Further, by adjusting the mist injection amount and the injection time, it is possible to easily control the cooling rate of the workpiece, which has been difficult with the conventional immersion type cooling apparatus.

JP-A-11-153386

However, the following problems exist in the above-described prior art.
In heat treatment of an object to be processed, the object to be processed may be cooled by a predetermined cooling pattern in order to transform the object to be processed into a predetermined structure. For example, depending on the type of the object to be treated, there is a type in which rapid cooling is performed in a certain period, while it is slowly cooled while maintaining uniformity of cooling in order to prevent the occurrence of distortion or bending in other periods. is there. In the prior art, cooling at such different cooling rates is performed by adjusting the mist injection amount and the injection time. However, when only the mist injection amount and the injection time are adjusted, it is difficult to cool at a wide range of cooling rates, and there is a possibility that a necessary cooling rate cannot be secured depending on the type of the object to be processed.

 The present invention has been made in consideration of the above points, and an object of the present invention is to provide a mist cooling device, a heat treatment device, and a mist cooling method capable of cooling an object to be processed at a wide range of cooling rates.

In order to solve the above problems, the present invention employs the following means.
The present invention is a mist cooling device for injecting and cooling a cooling mist on a heated workpiece, and includes a first nozzle that injects a cooling mist, and a cooling mist that is injected from the first nozzle. A configuration is adopted in which a second nozzle for injecting cooling mist having a particle size smaller than the particle size is employed.
In the present invention, since the particle size of the cooling mist injected from the first nozzle is larger than the particle size of the cooling mist injected from the second nozzle, the latent heat of vaporization per cooling mist particle of the first nozzle Is larger than the cooling mist of the second nozzle. Therefore, in the cooling using the first nozzle, it is possible to cool the workpiece more rapidly than using the second nozzle. On the other hand, in the cooling using the second nozzle, it is possible to perform the cooling more slowly while maintaining the uniformity of cooling than in the case of using the first nozzle.

 In the present invention, the first nozzle and the second nozzle diffuse and inject the cooling mist, and the diffusion angle of the cooling mist in the first nozzle is narrower than the diffusion angle of the cooling mist in the second nozzle. The configuration is adopted.

 Moreover, this invention employ | adopts the structure of having a control part which controls each injection amount of a 1st nozzle and a 2nd nozzle according to the cooling pattern of a to-be-processed object, respectively.

 Moreover, this invention employ | adopts the structure that a control part switches injection of the cooling mist between a 1st nozzle and a 2nd nozzle according to the cooling pattern of a to-be-processed object.

 In addition, the present invention employs a configuration in which the heat treatment apparatus performs heat treatment on an object to be processed and includes the mist cooling apparatus according to any one of claims 1 to 4.

The present invention is also a mist cooling method for injecting and cooling a cooling mist onto a heated object to be processed, the first nozzle for injecting the cooling mist, and the cooling mist to be injected from the first nozzle. And a second nozzle for injecting a cooling mist having a particle size smaller than that of the first particle size, and a cooling step for cooling the object to be processed.
In the present invention, since the particle size of the cooling mist injected from the first nozzle is larger than the particle size of the cooling mist injected from the second nozzle, the latent heat of vaporization per cooling mist particle of the first nozzle Is larger than the cooling mist of the second nozzle. Therefore, in the cooling using the first nozzle, it is possible to cool the workpiece more rapidly than using the second nozzle. On the other hand, in the cooling using the second nozzle, it is possible to perform the cooling more slowly while maintaining the uniformity of cooling than in the case of using the first nozzle.

According to the present invention, the following effects can be obtained.
According to the present invention, by providing the first nozzle that can be rapidly cooled and the second nozzle that can be slowly cooled while maintaining the uniformity of cooling, the workpiece to be heat-treated can be cooled at a wide range of cooling rates. There is an effect. Therefore, while performing rapid cooling in a certain period, there is an effect that it can be gradually cooled while maintaining the uniformity of cooling in order to prevent the occurrence of distortion and bending in other periods.

1 is an overall configuration diagram of a heat treatment apparatus 1. FIG. 2 is a schematic diagram showing a configuration of a cooling chamber 3. FIG. 3 is a schematic view of a first nozzle 35 and a second nozzle 45. FIG. 5 is a graph for explaining a heat treatment method for an object to be processed M; It is sectional drawing for demonstrating the temperature difference of the surface of the to-be-processed object M, and an inside.

 Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 5. In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size. In the following description, an example of a two-chamber heat treatment apparatus is shown as the heat treatment apparatus.

FIG. 1 is an overall configuration diagram of a heat treatment apparatus 1 according to the present embodiment.
The heat treatment apparatus 1 performs heat treatment such as quenching on the workpiece M, and includes a heating chamber 2 and a cooling chamber (mist cooling device) 3. The heating chamber 2 and the cooling chamber 3 are disposed adjacent to each other. A partition 4 that can be opened and closed is provided between the heating chamber 2 and the cooling chamber 3. When the partition wall 4 is opened, a transport path for transporting the workpiece M from the heating chamber 2 to the cooling chamber 3 is formed. When the partition wall 4 is shielded, the heating chamber 2 and the cooling chamber 3 are in a sealed state. .

 The workpiece M is subjected to heat treatment by the heat treatment apparatus 1 and is made of a metal material (including an alloy) such as steel containing a predetermined amount of carbon. The to-be-processed object M is transformed into a desired predetermined structure by heat treatment. Further, in order to prevent transformation to other than the target tissue and to uniformly transform the target tissue, cooling is performed by a predetermined cooling pattern (for example, a pattern having a rapid cooling period and a slow cooling period). In each drawing used in the following description, the workpiece M is shown in a rectangular parallelepiped shape, but there are various shapes and sizes, the number to be processed at one time, and the like. As the workpiece M, steel such as die steel (SKD material) and high-speed steel (SKH material) is targeted. In the present embodiment, die steel (SKD61) is exemplified as the workpiece M and will be described below.

Next, the structure of the cooling chamber 3 is demonstrated with reference to FIG.2 and FIG.3.
FIG. 2 is a schematic diagram illustrating a configuration of the cooling chamber 3 according to the present embodiment. 2 is a cross-sectional view taken along line AA in FIG. FIG. 3 is a schematic view of the first nozzle 35 and the second nozzle 45 installed in the cooling chamber 3, wherein (a) is a side view of the first nozzle 35, and (b) is a side view of the second nozzle 45. FIG.

As shown in FIG. 2, the cooling chamber 3 includes a container 10, a transport unit 20, a first cooling system 30, a second cooling system 40, a temperature measuring instrument 50, and a control unit 60. .
The container 10 constitutes an outer shell of the cooling chamber 3 and is a substantially cylindrical container that can form a sealed space inside. A liquefier (liquefaction trap) 11 for liquefying the cooling liquid vaporized by receiving heat from the workpiece M is installed at the upper part of the container 10.

 The transfer unit 20 is for carrying the workpiece M from the heating chamber 2 to the cooling chamber 3 and for carrying it out of the cooling chamber 3 to the outside, and in a direction parallel to the central axis of the container 10. M is conveyed. The conveyance unit 20 includes a pair of support frames 21, a plurality of conveyance rollers 22, and a roller driving unit (not shown).

 The pair of support frames 21 are erected on the inner bottom portion of the container 10 and support the workpiece M from below via a plurality of conveying rollers 22. The pair of support frames 21 are provided so as to extend in the conveyance direction of the workpiece M. The plurality of transport rollers 22 are configured to smoothly transport the workpiece M by rotating, and are provided on the mutually opposing surfaces of the pair of support frames 21 so as to be rotatable at predetermined intervals in the transport direction. ing. A roller driving unit (not shown) rotates the conveyance roller 22. In addition, the workpiece M of this embodiment is not directly placed on the transport roller 22 but is placed on the transport roller 22 via the tray 23. For the tray 23, for example, a mesh-like one or a plate material in which a plurality of holes (punching holes or the like) are formed is used in order to pass the cooling mist.

 The first cooling system 30 cools the workpiece M by spraying a coolant in a mist form on the workpiece M that is heated and provided in the container 10. The first cooling system 30 is used when the workpiece M is rapidly cooled. The first cooling system 30 includes a first recovery pipe 31, a first heat exchanger 32, a first pump 33, a first supply pipe 34, and a plurality of first nozzles 35. In addition, as a cooling fluid used, water, oil, salt, or a fluorine-type inert liquid etc. are used, for example.

 The first recovery pipe 31 is a pipe member that recovers the coolant supplied into the container 10 and the coolant re-liquefied by the liquefier 11 after being vaporized by heat received from the object M to be processed. Note that the coolant when being recovered in the first recovery pipe 31 is heated by heat received from the workpiece M. The first heat exchanger 32 is a heat exchanger that cools the recovered coolant.

 The first pump 33 discharges the coolant recovered from the container 10 and introduced into the first recovery pipe 31 to the first supply pipe 34 and flows toward the first nozzle 35. A first inverter 36 is connected to the first pump 33. The 1st inverter 36 drives the 1st pump 33 according to the directions of control part 60 mentioned below. A plurality of the first pumps 33 may be arranged in parallel with the first supply pipe 34. By arranging the plurality of first pumps 33 in parallel, it is possible to create a large flow rate that cannot be created by a single pump and to set a wide adjustment range of the flow rate of the coolant in the first cooling system 30. Become.

 The first supply pipe 34 is a pipe member that supplies the coolant discharged from the first pump 33 to a plurality of first nozzles 35 to be described later. A valve (not shown) for shutting off the supply of the coolant to the first nozzle 35 may be installed in the first supply pipe 34.

 The first nozzle 35 cools the workpiece M by spraying a mist-like cooling liquid (cooling mist) onto the workpiece M that is heated and provided in the container 10. The first nozzle 35 is used when the workpiece M is rapidly cooled. A plurality of first nozzles 35 are provided on the inner wall of the container 10 so as to surround the workpiece M, and a plurality of first nozzles 35 are provided side by side in the central axis direction of the container 10. This eliminates the portion of the workpiece M that is not exposed to mist as much as possible, and uniformly cools the workpiece M, thereby preventing the distortion of the workpiece M due to non-uniform cooling. Because.

 As shown in FIG. 3, the first nozzle 35 includes one injection port 35a, and diffuses and injects cooling mist from the injection port 35a. The particle size of the cooling mist injected from the first nozzle 35 is set larger than the particle size of the cooling mist injected from the second nozzle 45 described later. Since the particle size of the cooling mist injected from the first nozzle 35 is large, the amount of latent heat of vaporization of the mist per particle is large.

 The diffusion angle of the cooling mist that is diffused and ejected from the first nozzle 35 is set to about 15 °. The diffusion angle of the cooling mist in the first nozzle 35 is set to be narrower than the diffusion angle of the cooling mist in the second nozzle 45. The first nozzle 35 is installed on the inner wall of the container 10 such that the injection port 35 a faces the workpiece M installed in the container 10.

 As shown in FIG. 2, the second cooling system 40 cools the workpiece M by spraying a coolant in a mist form on the workpiece M that is heated and provided in the container 10. is there. The second cooling system 40 is used when the workpiece M is cooled slowly while maintaining the uniformity of the cooling of the workpiece M. The second cooling system 40 includes a second recovery pipe 41, a second heat exchanger 42, a second pump 43, a second supply pipe 44, and a plurality of second nozzles 45. In addition, as a cooling fluid used, water, oil, salt, or a fluorine-type inert liquid etc. are used, for example. Since the configuration of the second cooling system 40 other than the second nozzle 45 is the same as that of the first cooling system 30, the description thereof will be omitted, and the second nozzle 45 will be described below.

 The second nozzle 45 cools the workpiece M by spraying a mist-like cooling liquid (cooling mist) onto the workpiece M that is heated and provided in the container 10. The second nozzle 45 is used when the workpiece M is cooled slowly while maintaining the uniformity of cooling of the workpiece M. A plurality of the second nozzles 45 are provided on the inner wall of the container 10 so as to surround the workpiece M, and a plurality of the second nozzles 45 are provided side by side in the central axis direction of the container 10. This eliminates the portion of the workpiece M that is not exposed to mist as much as possible, and uniformly cools the workpiece M, thereby preventing the distortion of the workpiece M due to non-uniform cooling. Because.

 As shown in FIG. 3, the second nozzle 45 includes a plurality of (seven in this embodiment) injection ports 45a, and diffuses and injects cooling mist from the plurality of injection ports 45a. One of the plurality of injection ports 45a is arranged at the center of the tip of the second nozzle 45, and the other injection ports 45a are arranged side by side around the center of the tip. The particle size of the cooling mist injected from the second nozzle 45 is set smaller than the particle size of the cooling mist injected from the first nozzle 35. Since the particle size of the cooling mist injected from the second nozzle 45 is small, the amount of latent heat of vaporization of the mist per particle is small. Further, since the particle size of the cooling mist injected from the second nozzle 45 is small, the time during which the cooling mist injected from the second nozzle 45 stays in the container 10 is injected from the first nozzle 35. Longer than cooling mist. Furthermore, since the particle size of the cooling mist is small, the cooling mist injected from the second nozzle 45 can flow in the space in the container 10 more irregularly than the cooling mist injected from the first nozzle 35. .

 The diffusion angle of the cooling mist that is diffused and ejected from the second nozzle 45 is set to about 75 °. The diffusion angle of the cooling mist in the second nozzle 45 is set wider than the diffusion angle of the cooling mist in the first nozzle 35. The second nozzle 45 is installed on the inner wall of the container 10 such that the injection port 45 a located at the center of the plurality of injection ports 45 a faces the workpiece M installed in the container 10.

 The temperature measuring instrument 50 is a measuring instrument that is provided in the container 10 and can measure the surface temperature of the workpiece M being cooled in a non-contact manner. The temperature measuring instrument 50 is electrically connected (not shown) to the control unit 60, and a temperature measurement value is output to the control unit 60.

 The control unit 60 controls the driving of the first pump 33 via the first inverter 36 based on the temperature of the workpiece M measured by the temperature measuring device 50 according to the cooling pattern of the workpiece M and The driving of the second pump 43 is controlled via the two inverter 46. The controller 60 can individually control the driving of the first pump 33 and the second pump 43. Further, the control unit 60 can drive only one of the first pump 33 and the second pump 43.

 Further, the control unit 60 includes a data holding memory, and the memory holds the correlation between the supply amount of the cooling mist per unit time, the surface temperature of the workpiece M, and the internal temperature as table data. . The controller 60 is configured to be able to measure the internal temperature of the workpiece M from the measurement result of the temperature measuring device 50 (surface temperature of the workpiece M) using this table data. The correlation table data is created by, for example, preliminary experiments or simulations.

 Subsequently, in the heat treatment apparatus 1 according to the present embodiment, a procedure (cooling process) of cooling the heated workpiece M in the cooling chamber 3 will be described with reference to FIGS. 4 and 5. In the following description, a quenching process for transforming the workpiece M held at the quenching temperature into a martensitic structure will be described.

 FIG. 4 is a graph for explaining a heat treatment method for the workpiece M. In FIG. 4, the vertical axis represents temperature and the horizontal axis represents time. In FIG. 4, a solid line Ts indicates a temperature change on the surface of the workpiece M, and a broken line Tc indicates a temperature change inside the workpiece M.

 FIG. 5 is a cross-sectional view for explaining the temperature difference between the surface and the inside of the workpiece M. FIGS. 5A to 5C show the temperature distribution state of the workpiece M that changes sequentially with the passage of time in FIG. 4, and FIG. 5A shows the temperature distribution at time T1. 5B shows the temperature distribution at time T2, and FIG. 5C shows the temperature distribution at time T3. In FIG. 5, the high temperature and low temperature are indicated by the density of halftone dots.

 As shown in FIG. 4, in the heat treatment method of the present embodiment, first, the workpiece M heated to the austenite structure state (about 1000 ° C.) is in the vicinity of the transformation point Ms that starts to transform into a martensite structure. Cooling is performed from the time T0 to the target temperature Ta higher than the transformation point Ms using the first cooling system 30 (first quenching treatment S1).

 The target temperature Ta is set in a range lower than the transformation point Ps at which the workpiece M starts to transform into a pearlite structure and higher than the transformation point Ms at which the workpiece M begins to transform into a martensite structure. In this embodiment, since the workpiece M is die steel (SKD61), the target temperature Ta is set between 370 ° C and 550 ° C. Note that the target temperature Ta is preferably set to a temperature in the vicinity of the transformation point Ms (a temperature that is higher than the transformation point Ms by about tens of degrees Celsius) in consideration of a process in the second quenching process S4 described later.

 In the first rapid cooling process S1, the workpiece M is rapidly cooled by mist cooling to the target temperature Ta so as to avoid a transformation point Ps (so-called pearlite nose) that begins to transform into a pearlite structure. In the present embodiment, the workpiece M transported to the cooling chamber 3 is cooled by supplying and jetting a cooling liquid in a mist form from the first nozzle 35 in the first cooling system 30.

 The control unit 60 drives the first pump 33 via the first inverter 36. At this time, the second pump 43 of the second cooling system 40 is stopped. By driving the first pump 33, the coolant recovered from the container 10 and introduced into the first recovery pipe 31 is cooled by the first heat exchanger 32 and then sent out to the first supply pipe 34. The coolant flowing in the first supply pipe 34 is ejected from the plurality of first nozzles 35 in a mist form. Since the ejection port 35 a of the first nozzle 35 is provided to face the workpiece M, the cooling mist ejected from the first nozzle 35 adheres to the workpiece M. Since the attached cooling mist takes the vaporization latent heat from the workpiece M and vaporizes it, the workpiece M can be cooled.

 The particle size of the cooling mist injected from the first nozzle 35 is set to be larger than the particle size of the cooling mist injected from the second nozzle 45, and the amount of latent heat of vaporization of the mist per particle is increased. ing. Therefore, a large amount of latent heat of vaporization can be taken from the workpiece M, and the workpiece M can be rapidly cooled.

 The diffusion angle of the cooling mist that is diffused and ejected from the first nozzle 35 is set to about 15 °, and the diffusion angle of the cooling mist in the first nozzle 35 is the cooling mist in the second nozzle 45. Is set to be narrower than the diffusion angle. Therefore, the cooling mist sprayed from the first nozzle 35 can be efficiently applied to the workpiece M, and the workpiece M can be rapidly cooled.

 Here, since the basic cooling of the mist cooling is cooling from the surface side due to latent heat of vaporization, a temperature difference is generated on the surface and inside of the workpiece M depending on the degree of contact with the cooling mist (see FIG. 5A). ). For example, as indicated by the solid line Ts and the broken line Tc in FIG. 4, the temperature of the surface of the object to be processed M decreases in a shorter time than the temperature inside the object to be processed M. Becomes larger.

Next, in the heat treatment method of the present embodiment, the second cooling is performed when the measured temperature of the temperature measuring instrument 50 provided in the container 10 (that is, the surface temperature of the workpiece M) becomes lower than the target temperature Ta. The workpiece M is cooled by the system 40 (slow cooling process S2).
In the slow cooling process S2, the workpiece M is cooled by using the second cooling system 40 with a cooling efficiency lower than that of the first rapid cooling process S1. At this time, in the workpiece M, heat is transferred from the high temperature inside to the low temperature surface by heat conduction, so that the temperature difference between the surface and the inside becomes small.

 The control unit 60 stops driving the first pump 33 and drives the second pump 43 via the second inverter 46. That is, the pump to be driven is switched from the first pump 33 to the second pump 43 (adjustment step). By driving the second pump 43, the coolant recovered from the container 10 and introduced into the second recovery pipe 41 is cooled by the second heat exchanger 42 and then sent out to the second supply pipe 44. The coolant flowing in the second supply pipe 44 is ejected from the plurality of second nozzles 45 in a mist form. Since the second nozzle 45 is provided toward the workpiece M, the cooling mist sprayed from the second nozzle 45 adheres to the workpiece M. Since the attached cooling mist takes the vaporization latent heat from the workpiece M and vaporizes it, the workpiece M can be cooled.

 The particle size of the cooling mist injected from the second nozzle 45 is set to be smaller than the particle size of the cooling mist injected from the first nozzle 35, and the amount of latent heat of vaporization of the mist per particle is reduced. ing. For this reason, the amount of latent heat of vaporization taken away from the workpiece M is reduced, and the workpiece M can be slowly cooled. The amount of heat taken from the surface of the workpiece M is reduced, and heat is transferred from the high temperature inside to the low temperature surface by heat conduction, so that the temperature difference between the surface and the inside becomes small. That is, cooling can be performed while the temperature of the workpiece M is made uniform.

 The diffusion angle of the cooling mist that is diffused and ejected from the second nozzle 45 is set to about 75 °, and the diffusion angle of the cooling mist in the second nozzle 45 is the cooling mist in the first nozzle 35. It is set wider than the diffusion angle. In addition, since the particle size of the cooling mist is small, the cooling mist injected from the second nozzle 45 is more in the space in the container 10 than the cooling mist injected from the first nozzle 35. Can stay for a long time and flow irregularly. Accordingly, the cooling mist sprayed from the second nozzle 45 adheres to a portion where the cooling mist is difficult to adhere even if there is a portion where the cooling mist is difficult to adhere due to the size or shape of the workpiece M, for example. can do. That is, cooling can be performed while the temperature of the workpiece M is made uniform.

 In the slow cooling process S2, the entire temperature of the workpiece M becomes higher than the target temperature Ta due to heat conduction from the inside of the high temperature, and reaches the transformation point (for example, the transformation point Ps) of another target that is not intended. Implement cooling that does not cause streaking. That is, in the slow cooling process S2, cooling is performed so as to offset the temperature rise due to high-temperature internal heat conduction. In the slow cooling process S2, the cooling efficiency (the amount of cooling mist injected from the second nozzle 45) is controlled so that the surface temperature of the workpiece M does not reach the Ms transformation point due to the cooling. Adjust by means of part 60.

 The slow cooling process S2 is performed until the temperature inside the workpiece M becomes substantially equal to the target temperature Ta. Thereby, it can prevent that the temperature of the whole to-be-processed object M becomes higher than target temperature Ta. The temperature inside the workpiece M of the present embodiment is inquired using the measurement result of the temperature measuring instrument 50 provided in the container 10 and the table data recorded in the memory of the control unit 60. It measures by doing. As shown in FIG. 5B, the workpiece M that has undergone such a slow cooling treatment S2 has a relaxed surface and internal temperature distribution as compared to FIG. 5A.

Next, in the heat treatment method of the present embodiment, the supply of the cooling mist is stopped and the workpiece M is held for a predetermined time (holding process S3).
In the holding process S3, the supply of the cooling mist is stopped for a predetermined time, so that heat is transferred from the inside to the surface by heat conduction, and the temperature difference between the surface and the inside is further reduced. The mist cooling stop period of the holding process S3 is performed until the temperature difference between the surface and the inside of the workpiece M is within a predetermined threshold (for example, 10 ° C.). In the present embodiment, during the mist cooling stop period of the holding process S3, the surface of the workpiece M and the temperature inside the workpiece M are monitored using the table data in the temperature measuring device 50 and the control unit 60, and the workpiece M The process is terminated when the temperature difference between the surface and the interior of the substrate falls within a predetermined threshold.

 In the mist cooling stop period of the holding process S3, the temperature difference between the surface and the inside of the object to be processed M is determined from the temperature difference and the heat transfer coefficient of the surface and inside of the object to be processed M at the end of the slow cooling process S2. A method of predicting a time that falls within a predetermined threshold and terminating when the time has elapsed may be used. As shown in FIG. 5C, the workpiece M that has undergone such a holding process S3 is uniformized so that the surface and internal temperatures both become the target temperature Ta.

Finally, in the heat treatment method of the present embodiment, the workpiece M is cooled to a temperature not higher than the transformation point Ms (second rapid cooling process S4).
In the second quenching process S4, the workpiece M in a state in which the temperature difference between the surface and the interior is relaxed through the first quenching process S1, the slow cooling process S2, and the holding process S3 is cooled to the transformation point Ms or less. As a result, the surface and the internal structure of the workpiece M are transformed into a martensite structure almost simultaneously. In addition, if the target temperature Ta is a temperature that is higher than the transformation point Ms by about tens of degrees Celsius, the temperature difference between the surface and the inside of the workpiece M generated by the cooling in the second rapid cooling process S4 can be suppressed to a minute. In addition, generation of distortion and bending can be prevented and quality can be improved.

 In the second rapid cooling process S4, the workpiece M is rapidly cooled by mist cooling to a temperature equal to or lower than the transformation point Ms while avoiding the transformation point Bs that starts to transform into a bainite structure. In the present embodiment, also in the second rapid cooling process S <b> 4, the control unit 60 drives the first pump 33 via the first inverter 36 (adjustment process), and supplies the coolant from the first nozzle 35 in the first cooling system 30. Cooling is performed by supplying and spraying in a mist form. In other words, not only rapid cooling is required at the start of cooling but also cooling patterns that require rapid cooling of the workpiece M during the cooling process, cooling using the first cooling system 30 is performed. It is possible to cope with such a cooling pattern by carrying out a plurality of times.

In addition, about the cooling in 2nd rapid cooling process S4, when the temperature of the to-be-processed object M was fully separated from the transformation point Bs and it was not necessary to quench the to-be-processed object M, it used for example in the slow cooling process S2. The workpiece M may be cooled by the second cooling system 40.
The cooling process for transforming the structure into a martensite structure is completed by cooling the workpiece M of the present embodiment.

Therefore, according to the present embodiment, the following effects can be obtained.
According to this embodiment, by providing the first nozzle 35 that can be rapidly cooled and the second nozzle 45 that can be slowly cooled while maintaining the uniformity of cooling, the heated object M can be treated in a wide range. There is an effect that it can be cooled at a cooling rate. Therefore, while performing rapid cooling in a certain period, there is an effect that it can be gradually cooled while maintaining the uniformity of cooling in order to prevent the occurrence of distortion and bending in other periods.

 As described above, the preferred embodiments according to the present invention have been described with reference to the accompanying drawings, but the present invention is not limited to the examples. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

 For example, in the above-described embodiment, the diffusion angle of the cooling mist in the first nozzle 35 is set to be narrower than the diffusion angle of the cooling mist in the second nozzle 45, but the present invention is not limited to this. The diffusion angles may be equal only by giving a difference in the particle sizes of the mists for use.

 Moreover, in the said embodiment, although injection of the cooling mist is switched between the 1st nozzle 35 and the 2nd nozzle 45, it is not limited to this, From the 1st nozzle 35 and the 2nd nozzle 45 At the same time, the controller 60 may control and adjust each injection amount while spraying the cooling mist.

 Moreover, in the said embodiment, the 1st cooling system 30 which has the 1st nozzle 35, and the 2nd cooling system 40 which has the 2nd nozzle 45 are installed as a cooling system which injects a cooling liquid in the container 10 in mist form. However, the present invention is not limited to this, and both the first nozzle 35 and the second nozzle 45 may be provided in one cooling system. In this case, a predetermined injection amount adjusting unit that adjusts the injection amount from the first nozzle 35 and the second nozzle 45 is provided in the one cooling system.

 In the above embodiment, the holding process S3 that does not inject the cooling mist is provided. However, the present invention is not limited to this. After the slow cooling process S2, the holding process S3 is not performed. You may implement 2 quenching process S4.

DESCRIPTION OF SYMBOLS 1 ... Heat processing apparatus, 3 ... Cooling chamber (mist cooling apparatus), 35 ... 1st nozzle, 45 ... 2nd nozzle, 60 ... Control part, M ... To-be-processed object

Claims (6)

A mist cooling device that cools a heated object by injecting a cooling mist,
A first nozzle for injecting a cooling mist;
And a second nozzle for injecting cooling mist having a particle size smaller than that of the cooling mist injected from the first nozzle. The mist cooling device according to claim 1,
The first nozzle and the second nozzle diffuse and spray a cooling mist,
The mist cooling device according to claim 1, wherein a diffusion angle of the cooling mist in the first nozzle is narrower than a diffusion angle of the cooling mist in the second nozzle. The mist cooling device according to claim 1 or 2,
A mist cooling apparatus, comprising: a control unit that controls each of the ejection amounts of the first nozzle and the second nozzle according to a cooling pattern of the object to be processed. The mist cooling device according to claim 3,
The said control part switches the injection of cooling mist between the said 1st nozzle and the said 2nd nozzle according to the cooling pattern of the said to-be-processed object, The mist cooling apparatus characterized by the above-mentioned. A heat treatment apparatus for performing heat treatment on an object to be processed,
A heat treatment apparatus comprising the mist cooling apparatus according to any one of claims 1 to 4. A mist cooling method for cooling a heated workpiece by injecting cooling mist,
Cooling the workpiece using a first nozzle for injecting cooling mist and a second nozzle for injecting cooling mist having a particle size smaller than that of the cooling mist injected from the first nozzle. A mist cooling method, comprising: a cooling step.

Images